1. Field of the Invention
The present invention relates to a method of producing a tire carcass.
2. Description of the Related Art
Conventionally, in order to produce a tire carcass, a wide band-shaped member is formed by extruding a rubber from a large-sized extruder together with a plurality of cords that are coated by, and embedded in the rubber. The band-shaped member is then cut into pieces of a predetermined length by a dedicated cutter, and these pieces are successively joined with each other along their side edges that same parallel to the embedded cords, to thereby form a band-like carcass ply member in which the embedded cords are oriented in the width direction. The carcass ply member so prepared is wound around a roll and stored as a rolled body.
As another tire component member, an inner liner member is also formed by an extruder into a band-shaped member of a predetermined width, and wound around another roll and stored also as a rolled body. In this way, ply members and inner liner members have been conventionally produced separately and stored as separate rolled bodies. In a tire building process, the inner liner member is wound around a shaping drum and the ply member is then wound around the inner liner member, to thereby produce a cylindrical carcass.
The production of carcass ply members as described above requires many devices such as a large sized calender for forming a wide band-shaped member while coating rubber thereon, as well as a dedicated cutter, a joining device and a winding device, thereby resulting in large sized facilities and increased production man-hours and facility cost.
Furthermore, since carcass ply members and inner liner members are stored as rolled bodies, there may be caused fluctuation, for example, in the tire building precision due to deformation of the members or changes in tackiness thereof, thereby affecting on the tire quality.
There is also known a direct method in which a narrow band-shaped carcass ply member is formed by an extruder, and cut into pieces of a predetermined length, which are then successively adhered to or spirally wound around a drum. However, even in this case, the inner liner members are separately produced and wound around the drum in advance, thereby requiring a separate production step for the inner liner members as well as storage of the inner liner members as rolled bodies.
It is therefore an object of the present invention to eliminate the problems of the prior art as noted above, and provide an improved method of producing a tire carcass, which allows to downsize the facilities and reduce the production man-hours, while allowing production of a tire carcass of high quality at a reduced cost.
To achieve the aforementioned object, according to the present invention, there is provided a method of producing a tire carcass, comprising the steps of:
extruding from an extruder a narrow carcass ply member in which a plurality of cords are embedded in, and coated by a rubber material; and
simultaneously extruding from said extruder an inner liner member integrally with the carcass ply member, thereby forming a narrow band-shaped laminated body in which the inner liner member is integral with the carcass ply member.
According to the present invention, the double-layered band-shaped laminated body comprised of the carcass ply member and the inner liner member is formed by a simultaneous extrusion from an extruder, thereby allowing downsizing of the extruder as a whole. Furthermore, it is unnecessary to separately store the ply member and inner liner member as respective rolled bodies. This also allows the downsizing of the entire facilities, reduction of the production man-hours and reduction of the cost for the facilities. Furthermore, as the storage of rolled bodies is unnecessary, it is possible to avoid fluctuation, for example, in the tire building precision due to deformation of the members or change in tackiness thereof. It is thus possible to provide an improved quality of the product tires.
It is preferred that the inner liner member is extruded to have a required thickness at a required location of the band-shaped laminated body. In this instance, the carcass ply member is only locally formed with the inner liner member to minimize waste of the materials and reduce the cost.
The inner liner member may be intermittently extruded with a predetermined pitch in the extruding direction of said ply member. In this instance, the band-shaped laminated body has portions formed with the ply member and the inner liner member as a double-layered structure, and other portions that are of a single-layered structure without the inner liner member. The laminated body may be successively cut at the single-layered portions at a constant pitch into pieces which are then applied to the outer peripheral surface of a drum, thereby effectively producing a cylindrical carcass having an inner liner member only at a required portion.
The method of producing a tire carcass according to the present invention may further comprise the steps of cutting said band-shaped laminated body into pieces of a predetermined length, and applying said pieces onto the outer peripheral surface of a shaping drum, with the inner liner members and the ply members oriented radially inwards and outwards, respectively, while bringing said pieces into a side-by-side contact with each other, thereby forming a cylindrical carcass on the shaping drum. In this instance, a cylindrical carcass having an inner liner as the inner layer is formed directly on the shaping drum, to thereby efficiently produce tires. A resin sheet may be wound around the shaping drum, before the pieces are wound around the shaping drum. The resin sheet provides the function of a bladder upon vulcanization of a green tire, thereby realizing a so-called bladderless vulcanization.
Alternatively, the method of producing a tire carcass according to the present invention may further comprised the steps of cutting said band-shaped laminated body into pieces of a predetermined length, and arranging said pieces on a flat support so that said pieces are brought into a side-by-side contact with each other, to thereby form a flat carcass member. In this instance, it is possible to efficiently form the flat laminated body provided integrally with an inner liner member.
The band-shaped laminated body may be formed, along it side edges, with thin portions. In this instance, when the band-shaped laminated body is cut into pieces of a predetermined length and these pieces are wound on a drum in its circumferential direction, the side edges of the adjacent pieces may be in contact with each other or mutually overlapped at the thin portions so as to positively join the pieces without forming stepped portions, thereby improving the quality of the carcass.
The method of producing a tire carcass according to the present invention may further comprise the steps of spirally winding said band-shaped laminated body onto a drum and thereby forming a cylindrical member on the drum, cutting said cylindrical member in the axial direction of said drum, and subsequently developing the cylindrical member and thereby forming a flat carcass member. In this instance, it is possible to efficiently produce a double-layered flat laminated body including the carcass ply member and the inner liner member, and to wind the laminated body around a shaping drum thereby improving the productivity of the carcass.